Bevel protractor



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q 'im v z k m Feb. 28, 1950 -o. TREFZ BEVEL PROTRACTOR Original Filed July 18,- 1945 Patented Feb. 28, 1950 BEVEL PROTRACTOR Otto Trefz, Philadelphia, Pa.

Original application July 18, 1945, Serial No. 605,805. Divided and this application February 25, 1947, Serial No. 730,705

7 Claims.

This invention relates to bevel protractors and is particularly concerned with the provision of a device of this character, the adaptability of which is very much greater than that of any similar device heretofore known to those skilled in this art.

The invention has been developed with especial reference to its usefulness in adjusting the position of a machinists angle plate such, for example, as the improved angle plate which I have disclosed and claimed in my copending application Serial 605,805, filed July 18, 1945 (later issued as Patent 2,471,361), the present application, in fact, being a division of said earlier application.

The principal object of the invention is to provide a bevel protractor b means of which angular settings or adjustments involving machinists tools of various kinds can be more quickly, easily and accurately established than has been possible heretofore. The device also makes possible a wider range of adjustments as well as adjustments of finer degree.

How the foregoing objects, together with such other objects as may appear hereinafter or are incident to my invention, are attained is illustrated in preferred embodiments in the accompanying drawings wherein- Figure 1 is an elevational view of my improved bevel protractor;

Figure 2 is a side view;

Figure 3 is an elevational view illustrating the method in which the device may be employed in conveniently adjusting a machinists angle plate;

Figure 4 is a section on the line 4-4 of Figure 3; and

Figure 5 illustrates another way in which my improved device may be utilized. v

Referrin to the drawings it will be seen that my bevel protractor comprises a sine bar 81 associated with an index plate C. The sine bar is provided with a pair of spaced disks 88 and 89, the centers of which are located on a straight edge of the sine bar. These disks project laterally from one face of the bar and are spaced 3, given distance apart in accordance with well understood principles. For example, when the sine bar is laid out in accordance with the tables given in Oberg and Jones Machinery Handbook, 4th edition (1943) the disks will be A" in diameter and 5" apart so that the sine bar can be set at a desired angle by means of J ohansson blocks, as will now appear.

The index plate C is provided with an aperture 63 which is located off center as shown and struck from the center of this aperture are a series of radial graduations 68a, 68b, 68c, 68d, etc., all the way around a complete circle. These graduations, of course, can be arranged to any scale desired. Now, by referring to Figure 1 it will be seen that in setting the sine bar at a desired angle the disk 89 is placed in the aperture 63 of the plate C and is swung into registry with, let us say for example, the line 68b of the graduations on plate C, the sine bar in this position being shown in dot and dash lines. In this position it is then secured by means of a screw set clamping element working in a slot 9| in the sine bar. In order to check this setting, where unusually extreme accuracy is desired, a, spacer block 92 may be placed on the face plate 40, which spacer block is of a height exactly equal to the distance from the face plate to the lower periphery of the disk 89, as indicated by the dimension line y. Then Johansson blocks 93, the total dimension 2 of which is equal to the measurement given in the table above referred to for the angle desired, are placed between the spacer block 92 and the lower periphery of the disk 88 of the sine bar. If necessary, the clamp 90 is then loosened and the sine bar is moved whatever fraction may be required to bring the diskBB firmly into contact with the top Johansson block, whereupon the clamp is again tightened and the sine bar will be set exactly in the desired angular position.

The sine bar device which I employ may then be used to lay out angles of the exact degree for which it was set or it may be used, as illustrated in Figure 3, to obtain an exact setting of the angle plate A. For example, with the sine bar set at a 45 angle, such as illustrated in Figure 3, it is placed flatly against the under side of the plate 22 of the knee, proper adjustment to this position being eflected, for example, through use of the disk crank clamping member 31 and bolt 34a in the manner described in my copending application above referred to although an angle plate of usual construction may be employed if desired.

In Figure 5 I have shown the indexing plate C as resting on a different edge from that shown in Figure 1 and the sine bar in a position the reverse of that shown in Figure 1, which will demonstrate that my improved device may be accommodated to the setting and measuring of objects of various sizes and shapes and in each instance it is always possible to check them to J ohansson block accuracy by the use of the proper blocks at the dimensions y and z.

Vernier readings may be obtained with my improved bevel protractor by mounting a Vernier plate or segment 69 on the sine bar, as shown in Figures 3 and 4. This Vernier member can be mounted upon the sine bar in any suitable manner as, for example, by a friction fit, the member 69 being slipped over the free end of the sine bar. The inner end of the Vernier member is formed with a U-shaped section adapted to embrace the sine bar as seen to best advantage in Figure 4. In order to produce the friction a small U-shaped spring 691) is introduced between one leg of the U and the sine bar.

The Vernier member, of course, is provided with an arcuate Vernier scale H! which must be properly related to the graduations on the plate C. By way of example it will be assumed that the graduations on the vernier are of five minute spacing so that if the sine bar is rotated until the first graduation mark on the vernier registers with the line 680, the member to be positioned will have been moved 5 minutes. This, of course, is obvious to any one skilled in this art. It will be understood that the zero of the Vernier scale must be directly in line with the straight edge of the sine bar which passes through its button centers. It should also be noted that the rear edge of the Vernier segment is parallel to the straight edge of the sine bar which passes through the sine bar buttons and that its bottom edge (i. e. the edge opposite the vernier scale) is at right angles to the rear edge thus providing a square in my improved bevel protractor.

From the foregoing it will be apparent that the index plate C and the sine bar 81 constitute in effect a novel bevel protractor, the graduations on the plate radiating from the center of the circular aperture therein and the circular portions of buttons 88 and 89 of the sine bar having their centers located on a straight edge of the sine bar-either button, of course, being adapted to be inserted in the plate aperture. By locating the plate aperture off center as shown, as well as by making the plate sides absolutely square with respect to each other, the bevel protractor so constructed has a greatly increased range or field of usefulness as will be obvious to those skilled in the art.

I claim:

1. A bevel protractor comprising an index plate, a circular aperture therein from the center of which the graduations radiate, a cooperating sine bar the buttons of which project laterally from one face thereof and have their centers located on the straight edge thereof, said aperture being formed to receive and exactly fit a button, and clamping means constructed and arranged to secure the sine bar against the face of the plate in any desired position of angularity with one of the projecting buttons inserted in the aperture.

2. The protractor of claim 1 wherein the index plate is rectangular.

3. The protractor of claim 1 wherein the index plate is rectangular and wherein the aperture is off center.

4.. The protractor of claim 1 wherein the clamping means is carried by the sine bar.

5. The protractor of claim 1 wherein the clamping means is slidably carried in a longitudinal slot in the sine bar.

6. The protractor of claim 1 in which a Vernier segment is carried by the sine bar, the zero of which Vernier abuts the straight edge which passes through the button centers.

'7. The protractor of claim 1 in which a Vernier segment is carried by the sine bar, which segment has its rear edge parallel to the straight edge of the sine bar which passes through the sine bar buttons and its bottom edge at right angles thereto.

OTTO TREFZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 780,954 McCartney Jan. 24, 1905 1,308,451 Schachat July 1, 1919 1,366,396 Loefller Jan. 25, 1921 1,849,575 Huber Mar. 15, 1932 1,894,886 Paskowski Jan. 1'7, 1933 2,325,904 Brebeck Aug. 3, 1943 2,417,150 Berry Mar. 11, 194-7 FOREIGN PATENTS Number Country Date 504,651 England Apr. 28, 1939 

